Piston type shock absorbing and static load supporting drill string apparatus

ABSTRACT

Apparatus is disclosed for use in a drill string during rotary well drilling for supporting the static loads and for absorbing the shock loading imposed upon a drill bit. An improved separation element in the form of solid piston prevents migration of a shock absorbing gas into a liquid contained in the apparatus. The piston configuration and its annular seal arrangement solve a previously experienced gas migration problem. As a consequence, gas molecules are effectively excluded from regions where they otherwise interfere with normal operation of any components of the apparatus.

United States Patent Galle 1 July 17, 1973 PISTON TYPE SHOCK ABSORBING AND STATIC LOAD SUPPORTING DRILL STRING APPARATUS [75] Inventor: Edward M. Galle,Houston,Tex.

[73] Assignee: HughesToolCompany,l-louston,

Tex.

22 Filed: Nov. 5, 1971 211 Appl. 196.; 195,999

521 vs. (:1. 267/125 511 161.01 F16: 9/18 [58] Field of Search 267/125, 180, 71;

[56] References Cited UNITED STATES PATENTS 3,382,936 5/1968 Galle 175/321 3,606,297 9/1971 Webb 267/71 3,526,284 9/l970 Burge 175/321 Primary Examinerlames B. Marbert Attorney-R0bert A. Felsman 1 [57] ABSTRACT Apparatus is disclosed for use in a drill string during rotary well drilling for supporting the static loads and for absorbing the shock loading imposed upon a drill bitv An improved separation element in the form of solid piston prevents migration of a shock absorbing gas into a liquid contained in the apparatus. The piston configuration and its annular seal arrangement solve a previously experienced gas migration problem. As a consequence, gas molecules are effectively excluded from regions where they otherwise interfere with normal operation of any components of the apparatus.

8 Claims, 6 Drawing Figures PATENIED sum 2 0r 3 FIGURE 5 1 llllllllllllllllllllllllllllllllllllllllllllllllllllllll f0 H i 'l-llll' i FIGURE 6 EDWARD M. GALLE R. w m V m m FIGURE 3 ATTORNEY PISTON TYPE SHOCK ABSORBING AND STATIC LOAD SUPPORTING DRILL STRING APPARATUS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to rotary well drilling, particularly to the problem of decreasing shock loadings generated during forceful rotation of a drill bit against a borehole bottom.

2. Description of the Prior Art Previously, a number of types of shock absorbers have been developed for use in well drilling operations to prevent the upward transmission of shock loading through the drill string to the surface equipment used to rotate, as well as raise and lower, the drill string and bit. The advantages of decreasing shock loadings in a drill string during rotary well drilling are well known. In recent years several types of shock absorbers utilizing steel springs, rubber, or wire mesh have been available to the drilling industry. Although such tools have performed creditably, objectionable kelly bouncing still occurs under some drilling conditions. Some knowledgable observers conclude that longitudinal vibrations and cyclic forces could be better reduced if a shock absorber with a softer spring were used.

An apparatus which utilizes gas as a means to obtain a softer spring is disclosed in U.S. Pat. No. 3,382,936, entitled Shock Absorbing and Static Load Supporting Drill String Apparatus, patented May 14, 1968. While this tool displays many advantages associated with the use of a softer spring, it has disadvantages associated with the use of aflexible bag separation element that is intended to prevent comingling of gas and liquid inside the tool. The gas in such a tool may be subjected to an initial, charging pressure that exceeds 2,000 psi. When the tool is lowered in a well bore, the gas may be intentionally subjected to the hydrostatic pressure of the drilling fluid in the well bore, and as a result, the gas pressure may possibly reach 12,000 psi or more. Gas molecules tend to migrate through the flexible material of the separation element, which is usually a synthetic rubber. Accumulation of migrating gas has resulted in disadvantages, as for example, the rupture of a second flexible separation element used to separate the drilling fluid from a lubricating and pressure transmitting liquid inside the tool. Tool operation is thus limited.

SUMMARY OF THE INVENTION It is the general object of this invention to provide improved shock absorbing and static load supporting drill string apparatus.

Another object of the invention is to provide in static load supporting and shock absorbing drill string apparatus, improved means to separate a gas from a liquid used for lubricating purposes and to transmit to the gas the hydrostatic pressure of the fluid in a well bore.

Another object of the invention is to provide a solid type liquid gas separator in a shock absorbing and static load supporting drill string apparatus, such separator being impervious 'to migration of gas molecules.

In addition. it is a related object to provide sealing means including automatic lubrication of the sealing means used in combination with a solid, piston type separator for separating a gas and a liquid in a shock absorbing and static load supporting drill string apparatus.

In accordance with these objects, the invention may be summarized as an apparatus used for absorbing shock loadings generated during rotary well drilling, the apparatus employing an improved liquid-gas separation element having a solid, annular piston configuration. In its preferred form the piston confines on one side a gas and on the other side a liquid. The gas senses the hydrostatic pressure of the drilling fluid in the well bore and increases in the liquid pressure due to loads imposed upon the drill bit since the piston is free to move responsive to differential pressures. To more effectively prevent gas migration, the preferred piston has seal rings that minimize exposure of any material through which gas molecules may migrate. Further, the piston preferably includes wiper means on the end to prevent metalto-metal contact, and in addition, at least one passage is formed through the wall of the annular piston to provide access for a small amount of lubricant to the seal rings.

The above, as well as other objects, features and advantages of the invention will become apparent in the following description of a preferred embodiment of the invention.

DESCRIPTION OF THE DRAWINGS FIGS. 1, 2 and 3 are fragmentary side elevational views in longitudinal section which show a preferred embodiment of the improved shock absorbing and static load supporting drill string apparatus.

FIG. 4 is a side elevational view in longitudinal section showing a preferred embodiment of the improved separation element for the shock absorber.

FIG. 5 is a plan view of a retaining ring used inside the apparatus, as seen looking along the lines VV of FIG. 2. i

FIG. 6 is a fragmentary cross sectional view as seen looking along the line VIVI of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring initially to FIG. 1, a threaded portion 11 protrudes from a top sub l3'that forms a portion of a tubular body A that is thus adapted for attachment to a drill string member such as a drill collar (not shown).

An axial passage 15 extends through the top sub for transmitting a drilling fluid to a drill bit from suitable surface equipment (not shown).

A charging port or valve means 17 is carried by the top sub 13 for introducing a gas under selected pressure into the apparatus. Such port may be similar to that shown in US. Pat. No. 3,382,936, and functions generally the same as the valve used in a conventional automobile tire. The valve means thus extends through the top sub, which forms one part of the tubular body A and into a subsequently described gas region to enable selective variation of the charging pressure. A passage 19 extends toward the interior of the sub 13. Threads 2] are utilized to secure the top sub 13 to an upper barrel 23 of tubular body A.

Coaxially secured inside the upper barrel 23 to the top sub 13, and forming a part of the body, is a guide sleeve 25 retained by cap screws 27 that extend through a sealed ring 29 to the upper sub 13 and also through a flanged portion 31 of the guide sleeve. Passage 19 extends also through the metal ring 29 and flange 31. The purpose of the metal ring and its seals is to prevent leakage of fluid by the guide sleeve 25 and threads 21 associated with top sub 13. Axial passage also extends through the guide sleeve 25.

An annular and sealed cavity B is formed between the exterior annular surface 33 of the guide sleeve 25 and the interior annular surface 35 of the upper barrel 23. The cavity B is divided between a gas region 37 and a liquid region 41 by an improved movable and annular piston type separation element 39.

The piston 39 is adapted to move axially responsive to sensed pressure differential in gas region 37 and liquid region 41 for the purpose of equalizing the pressure in the gas region 37 and the liquid region 41.

In its preferred form the piston type separator 39 is constructed of a solid, fluid impervious metal of generally tubular configuration, with an enlarged region x, and an elongated region y.

As may be seen in FIG. 4, elongated region y is cylindrical with a wiper ring 43 that is preferably of Teflon received in a groove 45 and placed above an O- ring 47 in a groove 49, all of which are formed in a slightly enlarged portion 51 that extends inwardly beyond the inner wall 53 of region y.

A plurality of radially drilled holes 55 are formed through region y adjacent the enlarged region x of the piston to permit the interchange of lubricant that may be placed on the gas side of the piston to effect better lubrication of the various seal rings.

Enlarged region x has an inner seal means located in a groove 57 and comprises a pair of back-up rings 59 on either side of an O-ring 61. A similar seal arrangement 62 is on the exterior surface of the enlarged region x. A satisfactory O-ring 61 preferably may have, for example, a size of approximately inch thickness in the relaxed condition, a 70 Durometer, hardness, and be composed of a nitril rubber. Further, the backup rings 59 may be formed of a nitril rubber having a 90 Durometer hardness. The piston itself may be formed of an alloy 8620 A.I.S.I. steel, while the wiper ring 43 may be of a glass impregnated Teflon", having 15 percent glass. The purpose of the wiper ring is to prevent metal-to-metal contact with the exterior annular surface 33 of guide sleeve 25 to lessen wear.

A mandrel C has an end portion adapted for reciprocating movement along the interior cylindrical surface 60 of the guide sleeve 25. Seal 63 extends between the mandrel and the guide sleeve.

The lower region of the guide sleeve 25 is held in position by rings 65 and 67, as well as cap screws 69. As shown in FIG. 5, the cap screws 69 fill only a small number of the apertures 71 such that fluid may'flow by the ring.

The piston type separator 39 is adapted to float within cavity B responsive to sensed pressure differen tials, as previously explained. A lower shoulder 64 is sized to extend into an annular groove 66 (see FIG. 2)

- of the retainer ring 65, which together produce a dashpot effect when the separator 39 suddenly descends to its lowermost elevation. This avoids sudden stops of the separator and the lubricant that surrounds it and prevents excessive pressure differential across the seals of the separator. Hence, chances for damage of the seal means of the separator are decreased.

A bleeder port 73 extends radially through the upper barrel 23 for the purpose of bleeding air from inside the apparatus when a lubricating and pressure transmitting liquid is introduced into liquid region 41, as will be explained subsequently. A sealing plug 75 seals hole 73.

A snap ring 77 and washer 79 confine one end of a coil spring 81, the other end of which is confined by a washer 83, fastener 85, ring 87, suitably sealed as indicated by outer and inner seals 89 and 91. Ring 87 is moved upward if the fluid pressure differential acting on ring 87 exceeds the downward pressure exerted by the spring 81. If inner seal 91 moves from engagement with shoulder 92, fluid flows by the seal in the clearance space between the ring 87 and the wall 94 of the mandrel C. Hence the ring 87 and associated components form a valve means that can release liquid from region 41 when extension of ring 87 engages the top 98 of lower barrel 101 after the mandrel is unloaded and reaches its lowermost position. A passage 95 extends upward from a reservoir 97 and outward to the space between splines 99 and 102 (see FIG. 6), all of which cooperate to permit fluid to flow to or from region 41 when the valve means is opened.

Threads 104 secure the upper barrel 23 to a lower barrel 101, which confines a drilling fluid in a space 103 inside a flexible pressure compensating bag 105. Lubricating and pressure transmitting liquid is introduced to the reservoir 97 around the bag 105 through a liquid charging hole 107 which is sealed with a plug 109.

Referring to FIG. 3, the mandrel C has an enlarged lower portion 108 having seal rings 110 that seal against the interior surface 1 11 of the lower barrel 101. The compensator bag 105 arrangement may be of the same type shown in US. Pat. No. 3,382,936, having a vent hole 113 through which the drilling fluid may flow. Thus, the hydrostatic pressure of the drilling fluid in the annulus of the well bore is transmitted through the compensator bag tothe liquid in reservoir 97, and thus, to the liquid region 41 below the piston separator 39 and ultimately to the gas region 37 in cavity B.

A compensator bag retainer 115 supports the inner surfaces of the compensator bag 105, and is secured to mandrel C by a snap ring 117. Threaded apertures 119 may be utilized to extract the bag retainer 115 after removal of a snap ring 117. The mandrel terminates in a threaded portion 121, which may be secured to a drill string member.

A gas such as nitrogen is introduced through the charging port 17 (see FIG. 1), through passage 19 and into the gas region 37 of liquid-gas cavity B. As explained in US. Pat No. 3,382,936, a selected gas pressure of for example 2200 psi is induced on the gas in region 37.

A lubricating liquid is then introduced through the charge hole 107 after initial removal of the plug 109 and plug 75 until the pressure compensating bag 105 is essentially collapsed. This liquid fills the passage 95 in the mandrel, urging the valve means 87 upward until the liquid region 41 of cavity B is filled. Then seal plug 75 and plug 109 are reinserted.

As the apparatus is lowered in the well bore containing a drilling liquid, such liquid is introduced to the space 103 of the separator and pressure compensator bag 105 through the vent hole 113. This induces pressure on the lubricant in reservoir 97, as well as on the liquid in the space between splines 99, 102, and in the passage 95, and in the liquid and gas regions 41, 37 of cavity B. Since the piston 39 is free to move axially, the pressure of the gas in region 37 and the pressure of the liquid in region 41 are equalized. During drilling, shock loadings induced by rotation on the drill bit on the borehole bottom cause reciprocating movements of the mandrel C, the resulting shock loadings being absorbed by the gas in region 37.

If the apparatus is withdrawn from a well bore, the mandrel C is urged downward by the large pressure trapped in gas region 37, since the hydrostatic pressure continually decreases inside the separator and pressure compensator bag. 105 as the apparatus moves upward in the fluid in the well bore. Ultimately, the valve means 87 is opened when its lower portion 100 strikes the top 98 of lower barrel 101. Liquid may then flow from region 41, and passage 95 into the region 97 above the compensator bag 105. Thus, the pressure inside the apparatus is continually relieved until the apparatus reaches the surface. Only the initial charging pressure remains inside the gas region 37.

It should be apparent from the foregoing description that apparatus having significant advantages has been provided. The use of a solid piston separator prevents the migration of gas molecules from the gas region 37 to the liquid region 41. Since the piston is fabricated of a fluid impervious solid, the only possibility for leakage is around the seal rings associated with the piston. But since the cross sectional area of these seals is small, the possibility of gas'migration is minimal. The piston and seal configuration is beneficial in producing long sea] life. Moreover, the dash-pot effect achieved by using the preferred piston configuration prolongs sea] life.

While the invention has been shown in only one of its forms, it should be apparent to those skilled in the art that it is not so limited but is susceptible to various changes and modifications without departing from the spirit thereof. The invention may be utilized, for example in the two chamber apparatus shown in FIGS. 6 and 7 of [1.8. Pat. No. 3,382,936, which is but one of the possible modifications that will occur' to those of average skill in the art.

I claim: 1. Improved shock absorbing and static load supporting apparatus for use in a drill string, said apparatus comprising:

a tubular body adapted to be secured to a drill string member;

a mandrel reciprocably mounted to the tubular body for rotation therewith, and having an end portion adapted to be secured to another drill string memher;

the body and mandrel having passage means for a drilling fluid;

a gas and liquid cavity formed between the body and the mandrel with the body forming one end of said cavity and the mandrel forming the other end of said cavity;

an improved separation means dividing said cavity into gas and liquid regions;

valve means connected with said gas region for the introduction of a pressurized gas;

said separation means comprising a fluid impervious floating piston that equalizes pressure between the gas and liquid regions.

2. The apparatus defined by claim 1 in which the piston is annular, with sealing rings extending therefrom to opposed cylindrical surfaces in said body.

3. The apparatus defined by claim 2 wherein said piston is a metal and said sealing elements are resilient.

4. The apparatus defined by claim 2 wherein said piston comprises an enlarged annular region connected with an elongated region, the enlarged region having interior and exterior annular grooves containing resilient sealing rings, the elongated region having an annular groove facing a mating surface of the body, with a resilient ring therein, and passage means through the elongated region. v v

5. The apparatus defined by claim 4 wherein backup rings are disposed inthe grooves beside the sealing rings in the enlarged region of the piston.

6. The apparatus defined by claim 2 which further comprises vent means to transmit the hydrostatic pressure of the drilling fluid in a well bore to the fluids in said cavity.

7. The apparatus defined by claim 6 which further comprises a separator and pressuremeans connected with said vent means to prevent drilling fluid from reaching said liquid region of the gas and liquid cavity.

8. The apparatusdefined by claim 3 wherein a retainer ring is secured in said body beneath said piston, said ring having on one side an annular groove facing said piston with apertures extending from said groove through said piston, and said piston having an annular protrusion to mate with said groove. 

1. Improved shock absorbing and static load supporting apparatus for use in a drill string, said apparatus comprising: a tubular body adapted to be secured to a drill string member; a mandrel reciprocably mounted to the tubular body for rotation therewith, and having an end portion adapted to be secured to another drill string member; the body and mandrel having passage means for a drilling fluid; a gas and liquid cavity formed between the body and the mandrel with the body forming one end of said cavity and the mandrel forming the other end of said cavity; an improved separation means dividing said cavity into gas and liquid regions; valve means connected with said gas region for the introduction of a pressurized gas; said separation means comprising a fluid impervious floating piston that equalizes pressure between the gas and liquid regions.
 2. The apparatus defined by claim 1 in which the piston is annular, with sealing rings extending therefrom to opposed cylindrical surfaces in said body.
 3. The apparatus defined by claim 2 wherein said piston is a metal and said sealing elements are resilient.
 4. The apparatus defined by claim 2 wherein said piston comprises an enlarged annular region connected with an elongated region, the enlarged region having interior and exterior annular grooves containing resilient sealing rings, the elongated region having an annular groove facing a mating surface of the body, with a resilient ring therein, and passage means through the elongated region.
 5. The apparatus defined by claim 4 wherein backup rings are disposed in the grooves beside the sealing rings in the enlarged region of the piston.
 6. The apparatus defined by claim 2 which further comprises vent means to transmit the hydrostatic pressure of the drilling fluid in a well bore to the fluids in said cavity.
 7. The apparatus defined by claim 6 which further comprises a separator and pressure means connected with said vent means to prevent drilling fluid from reaching said liquid region of the gas and liquid cavity.
 8. The apparatus defined by claim 3 wherein a retainer ring is secured in said body beneath said piston, said ring having on one side an annular groove facing said piston with apertures extending from said groove through said piston, and said piston having an annular protrusion to mate with said groove. 